32,158 research outputs found
Design for waste-management system
Study was made and system defined for water-recovery and solid-waste processing for low-rise apartment complexes. System can be modified to conform with unique requirements of community, including hydrology, geology, and climate. Reclamation is accomplished by treatment process that features reverse-osmosis membranes
Polynomial treewidth forces a large grid-like-minor
Robertson and Seymour proved that every graph with sufficiently large
treewidth contains a large grid minor. However, the best known bound on the
treewidth that forces an grid minor is exponential in .
It is unknown whether polynomial treewidth suffices. We prove a result in this
direction. A \emph{grid-like-minor of order} in a graph is a set of
paths in whose intersection graph is bipartite and contains a
-minor. For example, the rows and columns of the
grid are a grid-like-minor of order . We prove that polynomial
treewidth forces a large grid-like-minor. In particular, every graph with
treewidth at least has a grid-like-minor of order
. As an application of this result, we prove that the cartesian product
contains a -minor whenever has treewidth at least
.Comment: v2: The bound in the main result has been improved by using the
Lovasz Local Lemma. v3: minor improvements, v4: final section rewritte
COMPETITIVE FORCES IN THE JAPANESE BEEF MARKET
This paper was presented at the INTERNATIONAL TRADE IN LIVESTOCK PRODUCTS SYMPOSIUM in Auckland, New Zealand, January 18-19, 2001. The Symposium was sponsored by: the International Agricultural Trade Research Consortium, the Venture Trust, Massey University, New Zealand, and the Centre for Applied Economics and Policy Studies, Massey University. Dietary changes, especially in developing countries, are driving a massive increase in demand for livestock products. The objective of this symposium was to examine the consequences of this phenomenon, which some have even called a "revolution." How are dietary patterns changing, and can increased demands for livestock products be satisfied from domestic resources? If so, at what cost? What will be the flow-on impacts, for example, in terms of increased demands for feedgrains and the pressures for change within marketing systems? A supply-side response has been the continued development of large-scale, urban-based industrial livestock production systems that in many cases give rise to environmental concerns. If additional imports seem required, where will they originate and what about food security in the importing regions? How might market access conditions be re-negotiated to make increased imports achievable? Other important issues discussed involved food safety, animal health and welfare and the adoption of biotechnology, and their interactions with the negotiation of reforms to domestic and trade policies. Individual papers from this conference are available on AgEcon Search. If you would like to see the complete agenda and set of papers from this conference, please visit the IATRC Symposium web page at: http://www1.umn.edu/iatrc.intro.htmInternational Relations/Trade, Marketing,
Point interactions in acoustics: one dimensional models
A one dimensional system made up of a compressible fluid and several
mechanical oscillators, coupled to the acoustic field in the fluid, is analyzed
for different settings of the oscillators array. The dynamical models are
formulated in terms of singular perturbations of the decoupled dynamics of the
acoustic field and the mechanical oscillators. Detailed spectral properties of
the generators of the dynamics are given for each model we consider. In the
case of a periodic array of mechanical oscillators it is shown that the energy
spectrum presents a band structure.Comment: revised version, 30 pages, 2 figure
Study of water recovery and solid waste processing for aerospace and domestic applications. Volume 2: Final report
The manner in which current and advanced technology can be applied to develop practical solutions to existing and emerging water supply and waste disposal problems is evaluated. An overview of water resource factors as they affect new community planning, and requirements imposed on residential waste treatment systems are presented. The results of equipment surveys contain information describing: commercially available devices and appliances designed to conserve water; devices and techniques for monitoring water quality and controlling back contamination; and advanced water and waste processing equipment. System concepts are developed and compared on the basis of current and projected costs. Economic evaluations are based on community populations of from 2,000 to 250,000. The most promising system concept is defined in sufficient depth to initiate detailed design
Jupiter: Its infrared spectrum from 10 to 40 microns
Spectral measurements of the thermal radiation from Jupiter in the 16-40 micrometer band were analyzed under the assumption that pressure broadened H2 transitions are responsible for the bulk of the infrared opacity over most of this spectral interval. Both the vertical pressure-temperature profile and the hydrogen mixing ratio were determined. The derived value of the molecular hydrogen mixing ratio, 0.89 + or - 0.11, is consistent with the solar value, 0.86
Automatic mapping of strip mine operations from spacecraft data
The author has identified the following significant results. Computer techniques were applied to process ERTS tapes acquired over coal mining operations in southeastern Ohio on 21 August 1972 and 3 September 1973. ERTS products obtained included geometrically-correct map overlays, at scales from 1:24,000 to 1:250,000, showing stripped earth, partially reclaimed earth, water, and natural vegetation. Computer-generated tables listing the area covered by each land-water category in square kilometers were also produced. By comparing these mapping products, the study demonstrates the capability of ERTS to monitor changes in the extent of stripping and reclamation. NASA C-130 photography acquired on 7 September 1973 when compared with the ERTS products generated from the 3 September 1973 tape established the categorization accuracy to be better than 90%. It is estimated that the stripping and reclamation maps and data were produced from the ERTS CCTs at a tenth of the cost of conventional techniques
Positive cosmological constant in loop quantum cosmology
The k=0 Friedmann Lemaitre Robertson Walker model with a positive
cosmological constant and a massless scalar field is analyzed in detail. If one
uses the scalar field as relational time, new features arise already in the
Hamiltonian framework of classical general relativity: In a finite interval of
relational time, the universe expands out to infinite proper time and zero
matter density. In the deparameterized quantum theory, the true Hamiltonian now
fails to be essentially self-adjoint both in the Wheeler DeWitt (WDW) approach
and in LQC. Irrespective of the choice of the self-adjoint extension, the big
bang singularity persists in the WDW theory while it is resolved and replaced
by a big bounce in loop quantum cosmology (LQC). Furthermore, the quantum
evolution is surprisingly insensitive to the choice of the self-adjoint
extension. This may be a special case of an yet to be discovered general
property of a certain class of symmetric operators that fail to be essentially
self-adjoint.Comment: 36 pages, 6 figures, RevTex
The role of regulatory mechanisms for control of plant diseases and food security — case studies from potato production in Britain
Being aware of the potentially devastating impacts of plant diseases on food security, governments have designed and employ plant health legislation to prevent or inhibit the worst impacts. The development of such policies in Britain, and latterly in Europe, can be closely linked to disease events that have occurred in the potato sector. We analyse early and current examples of policies governing potato diseases in Britain to identify the decision processes leading to the implementation of such phytosanitary policies and how they have evolved over time and in response to different disease threats. Reasons for developing and implementing phytosanitary policies include the desire to prevent pathogens being introduced (entering and establishing in a new area), the protection of export markets, and the lack of effective control measures. Circumstances in which regulatory policies would not be appropriate could include situations where a disease is already widely distributed, unacceptable costs, lack of exclusion measures, or difficulties of disease diagnosis. We conclude that in general, government policies have worked well in protecting British potato growing over the last one hundred years, despite of the failures of some of the policies discussed here. They have also contributed much to the development of plant health policies for other crops. Voluntary grower initiatives are a new mechanism complementing existing formal policies with an additional level of security that allows individual growers to take on additional responsibility rather than relying entirely on government legislation
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